3GPP (Third Generation Partnership Project) is a project in which specifications of mobile phone systems based on an evolved network of W-CDMA (wideband code division multiple access) and a GSM (global system for mobile communications) are studied and created.
In 3GPP, a W-CDMA scheme has been standardized as a 3rd generation cellular mobile communication scheme and its services have been sequentially initiated. Also, HSDPA (high-speed downlink packet access) having a higher communication rate has been standardized and its services have been initiated.
In 3GPP, EUTRA (evolved universal terrestrial radio access), which is the evolution of 3G radio access technology, has been studied.
FIG. 20 shows radio channels in EUTRA. A physical broadcast channel (PBCH), a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), a physical multicast channel (PMCH), a physical control format indicator channel (PCFICH), and a physical hybrid automatic repeat request (ARQ) indicator channel (PHICH) are used in a downlink through which signals are transmitted from a base station device 100′ to mobile station devices 200′a to 200′c. 
In EUTRA, a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a physical random access channel (PRACH) are used in an uplink through which signals are transmitted from the mobile station devices 200′a to 200′c to the base station device 100′.
FIGS. 2 and 3 are diagrams showing a method of arranging a physical resource block (PRB), which is an allocation unit for a user in EUTRA. In FIGS. 2 and 3, the horizontal axis represents time and the vertical axis represents frequency.
A radio frame to be identified by a system frame number (SFN) is constituted by 10 milliseconds (10 ms). One subframe is constituted by 1 millisecond (1 ms), and a radio frame includes 10 subframes #F0 to #F9.
As shown in FIG. 2, a PCFICH A11, a PHICH A12, a PDCCH A13, a physical downlink synchronization signal A14, a PBCH A15, a PDSCH/PMCH A16, and a downlink reference signal (RS) A17 are arranged in a radio frame to be used in the downlink.
As shown in FIG. 3, a PRACH A21, a PUCCH A22, a PUSCH A23, a downlink demodulation reference signal A24, and a downlink measurement reference signal A25 are arranged in a radio frame to be used in the uplink.
One subframe (for example, a subframe #F0) is separated into two slots #S0 and #S1. If a normal cyclic prefix (CP) is used, a downlink slot includes 7 orthogonal frequency division multiplex (OFDM) symbols (see FIG. 2), and an uplink slot includes 7 single carrier-frequency division multiple access (SC-FDMA) symbols (see FIG. 3).
If a long CP or an extended CP is used, a downlink slot includes 6 OFDM symbols, and an uplink slot includes 6 SC-FDMA symbols. In EUTRA, physical cell identity (ID) (PCI) information, which is information regarding a basic cell, is acquired by a cell search using a synchronization channel (SCH).
FIG. 4 shows an arrangement of the SCH in EUTRA. The SCH includes a primary SCH (P-SCH) and a secondary SCH (S-SCH). Positions of the P-SCH and S-SCH within a frame in EUTRA will be described.
As shown in FIG. 4, the P-SCH is arranged in last OFDM symbols of first slots of subframe numbers #0 and #5 in 6 resource blocks of the center of a system bandwidth, and slot synchronization is acquired. Next, the S-SCH is arranged on an OFDM symbol immediately before the P-SCH, and is used to acquire frame synchronization. A PCI is specified from a combination of a stream used in the P-SCH and a stream used in the S-SCH. In Non-Patent Document 2, the SCH is referred to as a synchronization signal, but the meaning is identical (Non-Patent Document 2).
In 3GPP, advanced-EUTRA, which performs communication at a higher transmission rate with backward compatibility directed to EUTRA, has been studied. In advanced-EUTRA, a plurality of band component carriers (CCs) through which communication can be performed through EUTRA are arranged in a frequency axis, and the introduction of an aggregation compositely using the band CCs has been studied.
One problem in executing the aggregation is the degradation of carrier metrics by a downlink reference signal. As a method of solving this problem, communication using a different PCI for each component carrier has been proposed (Non-Patent Document 3).
Another problem in executing the aggregation is an introduction method of a component carrier that is not recognized to a mobile station device of EUTRA. To solve this problem, the introduction of a component carrier in which no downlink synchronization signal is arranged as well as a component carrier having a downlink synchronization signal has been proposed (Non-Patent Document 4).
Non-Patent Document 1: GPP TS (Technical Specification) 36.300, V8.4.0 (2008-03), Technical Specification Group Radio Access Network, Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 8)
Non-Patent Document 2: 3GPP TS36.211, V8.4.0
Non-Patent Document 3: 3GPP TSG RAN WG1 #55, R1-084195, “Issues on the physical cell ID allocation to the aggregated component carriers,” LGE
Non-Patent Document 4: 3GPP TSG RAN WG1 Meeting #55, R1-084221, “Non-backward compatible component carriers for asymmetric carrier aggregation,” Panasonic